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Revisiting the Strike Capability Debate

Air Power Australia Analysis 2004-03
10th November 2004

A Paper
by Dr Carlo Kopp, MAIAA, MIEEE, PEng
Text © 2004 Carlo Kopp

F-35A SDD Prototype (Image via Air Force Link).


This paper revisits a series of key arguments in the Australian mass media, dealing with the late 2003 proposal to abandon White Paper planning for the RAAF force structure, and pursue an ad hoc strategy involving early retirement of the F-111. An abridged and serialised version of this paper appeared earlier 2004 in HeadsUp 308 newsletter and three subsequent issues. Given the popularity of the original series, APA Analyses is pleased to present the unabridged version in a single discussion paper.

In response to a critique published in HeadsUp 305 and 306, Chief of Air Force Air Marshal Houston submitted a rebuttal document to the Joint Standing Committee on Foreign Affairs, Defence and Trade. Dr Carlo Kopp responds to the rebuttal document with a counter-rebuttal.

Responding to the criticism of the RAAF exposing two F/A-18As instead of one F-111 in combat, the argument was raised that the F-111 does not provide redundancy, should the F-111 be lost or suffer a systems failure.

This may well be true, but the odds of two slower F/A-18As at 'high' altitude being detected and engaged near the missile launch point are greater than the odds of a single faster F-111 being detected at 200 ft AGL. In terms of systems failure induced aborts, the odds of a failure arising in one of two Hornets or their supporting tanker is greater than the odds of a like failure in one F-111. While the two Hornets have a greater chance of getting at least two JASSMs on target, they have a lower chance of getting all four on target.

The argument that a faster and lower flying F-111 is less exposed than the F/A-18A in the target area when launching JASSMs was challenged by a peculiar argument based on the idea of the F-111 being flown on a Lo-Lo-Lo profile, rather than the Hi-Lo-Hi profile one expects.

There is no evident tactical reason why an F-111 should be flown on a Lo-Lo-Lo profile as suggested in AM Houston's response, and asserting so suggests a poor understanding of missile delivery profiles by the author of the DoD response. Flying the F-111 on a Hi-Lo-Hi profile however does put it below the radar horizon of opposing ground based radars, and given the range of the JASSM possibly below the radar horizon of an opposing AWACS as well. The F/A-18A at 36,000 ft could be detected by a ground based radar at ~200 nautical miles, and by an AWACS at ~400 nautical miles, AWACS radar performance permitting. The F/A-18As' tanker could also be exposed.

In response to the criticism of the greater operational cost of using tanker supported F/A-18As vs unrefuelled F-111s, the argument was put that the F-111 is more expensive to run per airframe, and there is no saving in aircrew numbers when using two Hornets instead.

Factoring in the operational and crewing costs for 50% of the tanker required to support two Hornets, an F-111 could cost even more than twice as much to operate than a Hornet and still come out cheaper. Crunching numbers published by Defence for F/A-18A and F-111 annual costs, and US tanker costs, shows that the F/A-18A + tanker solution costs about 75% more than the unrefuelled F-111 does, per sortie.

In response to the observation that escort fighters are only required when there is a prospect that airborne Sukhois will be encountered, it was argued that air-air missiles should be carried on strike aircraft to complicate the options presented to an enemy, or otherwise face a mission abort or even be killed.

Having argued to no avail for many years that the RAAF should carry the ASRAAM missile on the F-111 instead of the Sidewinder, I am gratified to see the message is getting across finally! The ASRAAM does have an analogue interface port, compatible with the existing Sidewinder rails on the F-111.

The criticism of the radar/missile range inferiority of the F/A-18A vs the Su-30 was challenged with the argument that 'the Sukhoi does not have a decisive range advantage over an F/A-18'.

This is nonsense. The Sukhoi radars have about twice the antenna area of the F/A-18A's APG-73 radar, and transmit much more power – radar range performance is critically dependent on these two basic parameters. Given both radars are similar pulse Doppler technology, the Russian radar inevitably outperforms the smaller APG-73. In the recent Cope India exercise, Sukhois achieved parity in long range missile engagements against the F-15C, equipped with the larger Raytheon sibling to the F/A-18A radar, and generally acknowledged to be the best 3rd Western generation fighter in service.

The criticism of inferior weapon delivery capabilities provided by tanker constrained F/A-18A aircraft was challenged with the argument that only 16 F-111Cs are available from a nominal inventory of 27 F-111s, and that serviceability rates would further limit this number.

This argument presents problems in three areas. The first is that serviceability rates of F-111C/G demonstrated in the most recent Red Flag deployment approached 100% and exceeded newer types deployed, and in times of crisis maintenance tempo is always increased, therefore similar availability would apply. The second is that RF-111C aircraft will be Mil-Std-1760 capable and usable for precision weapons other than laser guided. The third is that were the F-111 retained, the Block C-4 SIP computer presents an economical means of putting a Mil-Std-1760 capability into the F-111G, and making all 27 'funded' F/RF-111C/G precision strike capable.

The argument that Australia needs an increase in strike capability was challenged with an argument that AEW&C, A330 tankers, an undefined 'network effect' and an 'improvement in data transfer' all somehow 'dramatically increase' strike capability.

These arguments contradict the reduction in total RAAF fleet strike capability at all ranges resulting from the loss of 30% of strike capable airframes, the impact of provisioning for spare tankers, and F/A-18A escorts for strike tasked F/A-18As, tankers and AEW&C aircraft. While networking with Link-16 can enhance survivability in strike operations, and Link-16/IDM networking can provide faster distribution of targeting coordinates and data, neither can increase the number of weapons which can be delivered against targets.

The argument that Link-16 and IDM networking equipment is becoming economical to retrofit into modern digital systems like the F-111C Block C-4 was challenged with a claim that 'considerable effort was required to integrate the AGM-142' into the '1960s architecture' of the F-111.

This is a nonsense, insofar as the AGM-142/Block C-4 system was integrated into the 1990s design AUP system, not the 1960s AJQ-20 analogue system replaced a decade ago. Moreover, current MIDS-LVT Link-16/TACAN terminals are designed to replace legacy TACAN installations with a single box, to minimise integration costs. IDM terminals are now available on a single VME card, hardware compatible with the spare slots in the new Block C-4 computer. Comparing the integration of Link-16 and IDM networking terminals to the AGM-142 upgrade is highly misleading.

The argument that adding new EWSP and networking to the F-111 was an incremental task was challenged with a lengthy treatise on the complexity of integration, with much emphasis on power, cooling and interfaces.

The power and cooling demands of form fit replacement Link-16 terminals like the MIDS-LVT are designed to match the legacy TACAN box they replace, so this is simply irrelevant, while demands of VME based IDM hardware are already covered in the Block C-4 SIP design. How complex any software might be is a function of how elaborate the sought functionality is – basic functions could be done for ~AU$3M or less, for a total project cost of ~AU$17M for 27 F-111s.

Observations on the ease of fitting the ALR-2002 warning receiver, designed to replace the legacy ALR-62, were challenged with the comment that 'this ... is focussed on physical dimensions and does not include the extensive cost and complexity of integration'.

Some years ago the RAAF paid for the full design, integration and flight testing of the ALR-2002 under the Block C-2A upgrade. Is it now the case that Defence have somehow managed to lose the resulting engineering and flight test reports, that all of this effort must be repeated again at full cost?

AM Houston's response to HU 306 is notable for the inclusion of misquotations and quotations out of context, which create a misleading impression of the original critique . Eg 'exchange rates [for close combat] have historically been below rates using ambush tactics, including modern BVR combat' becomes 'been at low rates using ambush tactics', incorrectly suggesting that HU 306 claimed poor BVR exchange rates.

The discussion of parameters favouring BVR capability was challenged with a treatise arguing the issues to be more complex than portrayed, introducing 'radar efficiency' into the argument, claiming the inferiority of the F-111, and arguing that 'bigger radars, longer ranging missiles, lower radar signatures and higher fuel loads' may contribute to BVR capability.

The radar literature does not identify 'efficiency' as a design parameter in pulse Doppler radars. Given the enormous investment now being put into high power phased array radars, ramjet and large diameter rocket motors for BVR missiles, stealth measures and conformal fuel tanks in current fighters, claiming these are not decisive to BVR combat challenges the collective wisdom of US, EU and Russian operators / manufacturers.

The point that fuel is energy and energy is life was challenged with the claim that the F-111 burns fuel at three times the rate of the F/A-18 in the 'high end air defence role'.

Given that US data shows the fuel burn of an F-111 at 0.95 Mach, 50% fuel and 28,000 ft to be about 15% greater than the fuel burn of an F/A-18 at 0.84 Mach, 50% fuel, loaded for air-to-air, this claim is unsupportable.

The point that speed was valuable in BVR combat was challenged with a claim that 'speed is only useful if it doesn't allow the threat aircraft to detect you before you can detect it'.

Given that air-air missiles have finite energy in their rocket motors and will run out of speed and manoeuvre capability as their motors burn out, claiming speed is less important than detection capability is simply nonsense. Knowing where a fast opponent is but being unable to engage due to inadequate speed performance has been a repeated feature of failed intercepts against Foxbats, SR-71s, Backfires, F-105s and F-111s over the years.

The observation that the F/A-22A does everything better than the JSF was challenged with a claim that 'the F/A-22A is not being developed to provide air to ground capability' .

This is simply not true. IOC configuration F/A-22A delivered in 2005 will carry a pair of JDAMs, synthetic aperture radar modes are in development, and in 2007 the aircraft acquires the GBU-39 Small Diameter Bomb, sized around the F/A-22A weapon bays, and datalink improvements. The F/A-22A will internally carry the same number of Small Diameter Bombs as the JSF does.

AM Houston's response to HU 306 raises technical points about the changes in F-111 radar cross section with 'small off boresight' angles and also claims that the smaller size of the F/A-18A gives it a smaller radar signature than an F-111.

Both statements are incorrect for X-band radar. The geometry of the F-111 presents its largest forward sector radar signature as a result of the engine inlets and radar bay bulkhead. Increasing the off-boresight angle left or right by only 8 degrees hides one inlet, and reduces the coupling aperture of the other. Radar signature for aircraft of similar size is mostly determined by shape, not by size, and the complex curvatures, concave reflectors and external stores of the F/A-18 are not conducive to effective radar signature reduction.

Observations on the retrofit of a new radar, internal missile launchers, stealth treatments and short wingtips (already under consideration) were challenged with claims of cost and risk, and it not being 'cost effective'.

The cost of all of these measures, other than the radar, is trivial in integration terms - internal trapeze launchers were integrated on the F-111 during the 1960s. Given the enormous strike/recce capability and support cost reduction gains from a modern AESA, complaints about cost-effectiveness are nonsense – BVR air-air capability is a bonus side effect.

Observations on the ~US$2.5M unit cost of modern AESA radars were challenged with a treatise on integration issues in the F/A-18, and claims that the radar hardware would be a 'small portion of the cost of integrating this radar on the aircraft'.

At this point, Chief of Air Force is effectively claiming that integration costs for a new radar on 27 F-111s would be several times greater than AU$100 million – effectively similar to 1990s AUP program costs. This is simply nonsense, as an industry sponsored study on a radar retrofit provided to Defence 3 years ago indicate that an AESA radar retrofit, including Terrain Following functions, and utilising existing TF computer, Pave Tack and F-111D HUD hardware, would be a relatively simple upgrade.

On escorting F-111s, Chief of Air Force's document cites out of context the opening comment on F-111 escort requirements, but does not cite the punchline in HU 306 ie 'only where airborne Sukhois are on station ...would it be necessary to escort the F-111', thereby creating a misleading impression of HU 306. On F/A-18 self-escort non-viability against Sukhois, the document states that 'Air Force does not believe that opposing regional fighters will have a detect first / shoot first / kill first advantage'.

This is not supportable comparing the F/A-18 vs Su-30, or either supported by Wedgetail, A-50 or other AWACS, a point later conceded in Hansard by Defence.

Chief of Air Force's document further argued that an F/A-18 will survive because it will be fitted with a datalink to receive threat information for AEW&C, but the F-111 would not as it would not be fitted.

Choosing not to fit a datalink and then claiming the F-111 cannot survive without it is a self fulfilling prophecy, one which could be remedied with less than AU$20M of investment.

The document further argues that higher fighter speed makes it easier to detect in low altitude clutter, incorrectly labelled as 'noise', unless terrain masking is used.

Aside from not mentioning the importance of defensive jammers on a penetrating aircraft under missile attack, the argument that high speed aids hostile detection is misleading, as it only applies for cases of closure rates between the target and interceptor placing the Doppler of the target outside the mainlobe and sidelobe clutter spectrum of the interceptor's radar. For most engagement geometries this is not true. Moreover many fighter lookdown-shootdown radars have much lower detection range against receding targets – NIIP's N-011M BARS on the Su-30 offers only 25% of the detection footprint compared to a closing target. What is also true is that Ground Control Intercept radars guiding interceptors will have serious problems in tracking fast low flying targets, and speed presents kinematic problems for interceptors and their missiles.

Air Power Australia Analyses  ISSN 1832-2433
Australia's First Online Journal Covering Air Power Issues

People's Liberation Army Air Power Index Page [Click for more ...]
Military Ethics, Culture, Education and Training Index Page [Click for more ...]
Russian / Soviet Weapon Systems Index Page [Click for more ...]

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